1. Field of the Invention
This invention relates to a liquid crystal display, and more particularly to a driving method and apparatus for a liquid crystal display having a picture with a contrast ratio.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) controls light transmittance of liquid crystal cells in accordance with video signals to thereby display a picture. Such an LCD has been implemented in an active matrix structure having a switching device associated with each cell. LCDs have been applied to display devices such as computer monitors, office equipments, cellular phones, and the like. The switching device for the active matrix LCD mainly includes a thin film transistor (TFT).
FIG. 1 is a schematic block diagram of a configuration of a driving apparatus for a liquid crystal display in accordance with related art. Referring to FIG. 1, the related art LCD driving apparatus includes a liquid crystal display panel 2 having an m×n number of liquid crystal cells Clc arranged in a matrix structure, an m number of data lines D1 to Dm and an n number of gate lines G1 to Gn crossing each other and thin film transistors TFT provided adjacent to the crossings, a data driver 4 that applies data signals to the data lines D1 to Dm of the liquid crystal display panel 2, a gate driver 6 that applies scanning signals to the gate lines G1 to Gn, a gamma voltage supplier 8 that supplies the data driver 4 with gamma voltages, a timing controller 10 that controls the data driver 4 and the gate driver 6 using synchronizing signals from a system 20, a direct current to direct current converter 14, hereinafter “DC/DC converter”, that generates voltages supplied to the liquid crystal display panel 2 using a voltage from a power supply 12, and an inverter 16 that drives a back light 18. The system 20 applies a plurality of signals to the timing controller. The applied signals include vertical/horizontal signals Vsync and Hsync, clock signals DCLK, a data enable signal DE and R, G and B data.
The liquid crystal display panel 2 includes a plurality of liquid crystal cells Clc arranged in a matrix structure at crossings of the data lines D1 to Dm and the gate lines G1 to Gn. The thin film transistor TFT provided at each liquid crystal cell Clc applies a data signal from each data line D1 to Dm to the liquid crystal cell Clc in response to a scanning signal from the gate line G. Further, each liquid crystal cell Clc is provided with a storage capacitor Cst. The storage capacitor Cst is provided between a pixel electrode of the liquid crystal cell Clc and a pre-stage gate line to thereby keep constant a voltage of the liquid crystal cell Clc. Alternatively, the storage capacitor Cst can be provided between the pixel electrode of the liquid crystal cell Clc and a common electrode line.
The gamma voltage supplier 8 applies a plurality of gamma voltages to the data driver 4. The data driver 4 converts digital video data R (Red), G (Green) and B (Blue) into analog gamma voltages (i.e., data signals) corresponding to gray level values in response to a control signal CS from the timing controller 10, and applies the analog gamma voltages to the data lines D1 to Dm.
The gate driver 6 sequentially applies a scanning pulse to the gate lines G1 to Gn in response to a control signal CS from the timing controller 10 to thereby select horizontal lines of the liquid crystal display panel 2 supplied with the data signals.
The timing controller 10 generates the control signals CS that controls the gate driver 6 and the data driver 4 using the vertical/horizontal synchronizing signals Vsync and Hsync and the clock signal DCLK input from the system 20. Herein, the control signal CS that controls the gate driver 6 comprises a gate start pulse GSP, a gate shift clock GSC and a gate output enable signal GOE, etc. Further, the control signal CS that controls the data driver 4 comprises a source start pulse SSP, a source shift clock SSC, a source output enable signal SOE and a polarity signal POL. Etc. The timing controller 10 re-aligns the R, G and B data from the system 20. The timing controller applies the re-aligned R, G and B data to the data driver 4.
The DC/DC converter 14 boosts or drops the level of a voltage input from the power supply 12 from a value of 3.3V. The DC/DC converter supplies the converted voltage to the liquid crystal display panel 2. Such a DC/DC converter 14 generates a gamma reference voltage, a gate high voltage VGH, a gate low voltage VGL and a common voltage Vcom, etc.
The inverter 16 drives the back light 18 to the back light 18 by applying a driving voltage (or driving current). The back light 18 generates light in accordance with the driving voltage (or driving current) from the inverter 16 and applies the generated light to the liquid crystal display panel 2.
To display a vivid image on the liquid crystal display panel 2 driven in this manner, a distinct contrast between brightness and darkness of a data must be represented. However, since the related art does not disclose a method of rendering a distinct contrast of the data, it is difficult to display a vivid image using the related art liquid crystal display panel. Furthermore, since the related art back light 18 produced a constant brightness level irrespective of the input data, it is difficult to display a dynamic and fresh image using the related art back light unit.